Process of treating cobalt-tung-sten-chromium alloys



Patented Jan. 14,1936

UNITED STATES PROCESS OF TREATING COBALT-TUNG- STEN-CHROMIUM ALLOYS Werner Kiister, Krefeld, Germany, assignor to Vereinigte Stahlwerke Aktiengesellschait,

Dusseldorf, Germany No Drawing. Application May 4, 1934, Serial No. 723,976. In Germany February 18, 1931 2 Claims. 01. 14.8-11.5)

Exhaustive experiments have demonstrated 5 that alloys containing. about 40 to 85% of cobalt,

about 5 to 40% of tungsten and the balance constituting about to 40% of the alloy consisting substantially of chromium, if they contain carbon in amounts not exceeding 0.3% are very well 10 adapted to be precipitation hardened by a special heat treatment, namely by heating the cast or rolled alloys to a temperature between about 1000 C. and the melting point 01' the alloy followed by quenching in the air, water or oil, and

5 then heating the quenched alloys at temperatures between 500 and 900 C. By this treatment, the mechanical properties of the alloys are very considerably improved by comparison with what they were prior to the heat treatment and particularly 20 good hardness values ensue, ii the alloys contain chromium in addition to cobalt and tungsten in the proportions mentioned. A furtherimprovement in the quality of the alloys occurs on the tungsten content being increased to above 25 10%. The chromium content lies preferably below 40%. Moreover, thealloys may contain up to of other additions such as molybdenum, manganese, nickel, iron, copper, aluminium, vanadium or titanium, without affecting the scope of the 30 invention, such small additions are compris d by the termin the claims: the balance consisting substantially of chromium".

The following examples serve to illustrate more clearly the nature of the present invention:-

1. An alloy of cobalt 49%, tungsten 38%, chromium 12%, vanadium 1% and carbon 0.1%, gave a hardness of 410 Brinell units aiter quenching from 1200 C., and a hardness of 680 Brinell units after subsequent annealing at 800 C. for 4 hours.

2. An alloy of cobalt 41%, tungsten 28%, chromium 27%, vanadium 1.5% and carbon 0.1%, gave a hardness of 336 Brinell units after quenching from 1200 C., and a hardness of 660 Brinell units after annealing at 850 C. for an hour.

3. An alloy of: cobalt 56%, tungsten 26%, chromium 13%, iron 4.5%, vanadium 0.6% and carbon 0.06%, gave a hardness of 315 Brinell units after quenching from 1200 C. and a hardness of 545 Brinell units after annealing at 800 C. for an hour.

What I claim and desire to secure by Letters Patent in the United States is:

1. The process which consists in forming an alloy comprising about 40 to 85% cobalt, about 5 to 40% of tungsten and the balance constituting about 10 to 40% of the alloy consisting substantially of chromium, said alloy containing carbon in amounts not exceeding 0.3%, subjecting said alloy to a precipitation hardening by heating the alloy to a temperature between about 1000 C. and the melting point of the alloy, rapidly cooling from this temperature and annealing at temperatures between 500 and 900 C.

2. An alloy comprising about 40 to 85% cobalt, 5 to 40% tungsten and as balance constituting about 10 to 40% of the alloy substantially chromium, said alloy containing carbon in amounts not exceeding 0.3% and being hardened by precipitation hardening to such an extent that its hardness has been raised by at least 200 to 300 Brinell units.

WERNER 1:65am. 

